Process and apparatus for preventing loss of drilling fluid



March 31, 1959 Filed March 4, .1955

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A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID 6Sheets-Sheet 1 Arden H. Dawson, Jr. INVENTOR.

BY MM 3% P ocEss AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID A.'H. DAWSON, JR

March 31 1959 6 Sheets-Sheet ?2 Filed March 4, 1955 6 Sheets-Sheet 3 TL7 w III! Fig 8 Arden H. Daws on, Jr.

March 31, 1959 A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID Filed March4, 1955 March 31; 1959 A. H. DAWSON, JR 2,879,846

PRQCESSANI. APPARATUS FDR PREVENTING LOSS OF DRILLING FLUID 6Sheets-Sheet 4 Filed March 4, 1955 Arden H. Dawson, Jr.

IN VEN TOR.

BY W-fin March 31, 1959 A. H. DAWSON, JR

PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID 6Sheets-Sheet 5 Filed March 4,' 1955 Arden H. Dawson, .lr.

uvmvrox.

BY on! March 31, 1959 A. H. DAwsoN, JR 2,879,846

. PROCESS AND APPARATUS FOR PREVENTING LOSS OF DRILLING FLUID v FiledMarch 4, 1955 6 Sheets-Sheet 6 i 'j Fig. /8 Fig.l6 5' 220 o 26 p242 46 o48 262 -264 I o v 252- I ;22 ,4 220 224 i 2 1 255 254 Em 226 3 j i 450 Z2 232 i GEE); 24a i 246 2 2 244 1 Z 1 v f o I 4 I 230 Q a o '26 -48 2 go228 22a 44 a 2 7 Q o o 4 2 a 2 O Q /7 o A Fig. /9

, Arden H. Dawson, Jr. M INVENTOR.

l 3 3 BY @4052. min aw Em United States Patent PROCESS AND APPARATUS FORPREVENTING LOSS OF DRILLING FLUID Arden H. Dawson, In, Texhoma, Okla.

Application March 4, 1955, Serial No. 492,174 19 Claims. (Cl. 166-23)This invention comprises novel and useful improvements in a process andapparatus for preventing loss of circulation of drilling fluids and morespecifically relates to novel methods and apparatuses whereby lostcirculation materials in the form of drilling mud additives may bemechanically introduced in relatively high concentrations directly at aregion of a thief formation at which cirulation losses are occurring.

The present application comprises a continuation-inpart of my priorcopending application, Serial No. 345,- 447, filed March 30, 1953, nowUS. Patent No. 2,815,- 190, issued December 3, 1957, and bearing thesame title as that of the present application.

The general purpose of this invention is to provide apparatuses andmethods whereby the sealing of a porous formation may be effected withas much precision and certainty, and with as little delay, as possible.

The principal object of this invention is to provide a method andapparatus whereby concentrations of drilling mud additives, and inparticular, such concentrations which are in excess of those which arecapable of being 'handled by conventional drilling fluid pumps, may beintroduced into a well bore for sealing porous formations.

A further object of the invention is to provide a method and apparatuswherein the concentration of drilling mud additives in a drilling fluid,as delivered by conventional drilling fluid pumps into a mud circulationsystem,

may be greatly increased at a predetermined region of a thievingformation to effect, by the increased concentration, a more eflicientsealing action upon the porous formation.

Yet another purpose of the invention is to provide a process andapparatus in conformity with the foregoing objects wherein theconcentration of a drilling mud additive or lost circulation material ina drilling fluid may 'be temperarily increased at a predetermined regionof a well bore to effect a more efficient sealing of a porous or leakyformation therein.

A still further object is to provide an apparatus and method wherebyslugs or plugs of lost circulation material, at various desiredconcentrations, may be formed and delivered to a formation by aconventional mud cir' culating system, and without any limit to theconcentration of the lost circulation material being imposed by theelements of the mud circulatory system.

An additional important object of the invention is to provide a methodand apparatus whereby a constant flow at a uniform rate of a givenconcentration of a drilling mud additive in a drilling mud may beintroduced into the circulating systemand whereby, within the well bore,a quantity of the drilling mud additive may be concentrated andcontinuously or intermittently delivered in highly concentrated form toa predetermined portion of a well bore to seal porous formationstherein.

A further primary object of the invention is to provide a process andapparatus whereby conventional drilling fluid pumps may be renderedeflective to deliver considice erably greater concentrations of drillingmud additives or lost circulation materials in a drilling fluid than hadbeen heretofore possible.

Still further important objects of the invention are to provideapparatuses and methods whereby lost circulation material may becontinuously supplied into the drilling fluid circulating system of awell by conventional mud circulating pumps therefor, and at a degree ofconcentration of the lost circulation material which is consistent withpresent practice, and yet wherein a predetermined but variablyadjustable increase in the concentration of the lost circulationmaterial may be obtained for discharge into the well bore at a selectedlocation therein to more effectively seal a thief or porous formation byvirtue of the controlled increase in the concentration or density of thelost circulation material. f

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

Figure 1 is a somewhat diagrammatic view, parts being broken away andshown in section, of the well bore showing an apparatus in accordancewith the present invention applied thereto;

Figure 2 is an enlarged elevational view, parts being broken away andshown in vertical section, of a concentrating device for increasing theconcentration of drilling mud additives in drilling mud;

Figure 3 is a vertical sectional detail view, taken upon upon anenlarged scale, substantially upon the plane indicated by the sectionline 4-4 of Figure 2;

Figure 5 is a view similar to Figure 2, but of a second embodiment ofthe mud additive concentrating and discharging device;

Figure 6 is a view similar to Figure 2 but showing a third embodiment ofthe concentrating device, a part thereof being broken away;

Figure 7 is a view similar to Figure 2, but showing another or fourthembodiment of a concentrating device, a part thereof being broken away;

Figure 8 is a view of the embodiment of Figure 7, but showing the samein a position for discharging a concentration of drilling mud additives;

Figure 9 is a view similar to Figure 2, but showing still another orfifthembodiment of a concentrating device, a part thereof being brokenaway;

Figures 10 and 11 are views similar to Figure 2, showing still furthersixth and seventh embodiments of the concentrating device, parts thereofbeing broken away;

Figure 12 is a perspective view of the means for dischargingconcentrated lost circulation material from the concentrating devices ofFigures 2, 5 and 6;

Figure 13 is a view similar to Figure 2 but showing an eighth embodimentof the concentrating device;

Figure 14 is a detail view taken in horizontal section substantiallyupon the plane indicated by the section line 14-14 of Figure 13;

Figure 15 is a fragmentary view in vertical section of a ninthembodiment of the concentrating device, being a slight modification ofthe structure of Figure 13;

Figure 16 is a view in vertical section of a tenth embodiment of theconcentrating device in accordance with this invention; v

Figure 17 is a detail view upon an enlarged scale taken in verticalsection substantially upon the plane indicated by the section line17---17 of Figure 16;

Figure 18 is a detail view taken upon an enlarged scale and in verticalsection of the swivel connection by which the concentrating device iscarried by the drill string; and

Figure 19 is a detail view in vertical section of the modifiedconstructionof the lower end of the, concentrating device of Figures, 16and 17..

It is well known in the oil well drilling industry that the maintainingof a continuous circulation in the well bore of a drilling fluid,commonly known as drilling mud, is essential for eflicient andeconomical drilling operations. Further, it is common knowledge that thewell driller is often confronted by serious problems resulting from twobasic types of drilling fluid losses into formations penetrated by thewell bore.

The first of these losses, commonly referred to as water-loss orfiltration involves a relatively small, slow loss of the filtrateduring. filtration of a drilling fluid by certain, finely porous,filter-like formations. Waterloss may be controlled almost as desired byregulating the composition or properties of the drilling fluid, therebyregulating the sealing action. of the residue, commonly known aswall-cake which is deposited upon the filtermg surface of such strataduring this filtration process. The control of water-loss is very oftenextremely important, but practically no difficulty in maintainingcirculation of drilling fluid is presented due to water-loss.

The second type of loss, commonly referred to as loss of circulation orlost returns occurs due to penetration by the well bore of porous orleaky formations, sometimes called thief formations or lost circulationzones, containing permeable pore spaces, fractures, faults, fissures,cavities and the like which are relatively large, causingcorrespondingly large and rapid losses of drilling fluid. Loss ofcirculation may result due to permeable pore spaces ranging in size fromthose immediately larger than will effectively filter dispersedcolloidal material from a colloidal suspension or drilling fluid, as inthe foregoing filtration process which results in water loss, to verylarge caves and caverns which may contain migrating water or communicatewith the atmosphere. Improper handling of drilling fluids or heavy mudsmay break down certain formations, compress unconsolidated strata orlift overburden to form cavities which cause loss of circulation. Lossof circulation is a problem in itself, but may result in a number ofother fatal effects upon the well drilling operation.

In order to attempt to prevent loss of circulation, it has becomecustomary to introduce drilling mud additives commonly known as lostcirculation materials into the drilling mud for the purpose of sealingor clogging the porous, thief formations with such material and therebyprevent loss of the drilling fluid into such formations. Variousmaterials have been employed for this purpose with varying degrees ofsuccess.

In general, however, it is desirable to employ as great a concentrationof the lost circulation materials in the drilling fluid as can behandled, by the pumps and other elements of the drilling mud circulatingsystem, without excessive difficulty. Obviously, a greater concentrationof the drilling mud additive at a leaky formation will more quickly andmore certainly seal and plug the same, preventing further loss ofcirculation and permitting the normal drilling operation to becontinued. However, in present systems for circulating drilling fluids,there are definite limits to the amounts or concentrations of lostcirculation material which may be employed therein. Thus, an unduly highconcentration of such material will tend to clog the pumps, and otherelements of the system, necessitating shutdowns while the obstructionsare cleaned therefrom. In general, therefore, it may be stated that theconcentration of the drilling mud additives in the drilling mud has arelatively constant limit imposed or determined by the characteristicsof the mud pumps and other elements of they drilling fluid circulatorysystem.

The present invention aims to overcome these difliculties by devising aprocess and an apparatus whereby lost circulation material may bedischarged in a well bore in concentrations which are independent of thecapacities of the mud pumps, valves and other elements of a drillingfluid circulator system.

Embodiment of Figures 1-4 and 12 Reference is now made first to Figures1-4 and 12 "which show one satisfactory embodiment of apparatus forpracticing the principles of this invention. The numeral 10 designatesin general a drilling rig of any conventional design for operating adrilling pipe or drill stem 12 which is positioned inside the well bore14. At its lower end, the drill pipe 12 has swivelly attached thereto aconcentrating device indicated generally by the numeral 16 and of aconstruction to be set forth hereafter, an anchor or tail pipe 18 beingdisposed below and carried by the concentrating device. In the view ofFigure 1, the drill pipe is shown as lowered in the well with the anchorpipe 18 resting upon the bottom of the same.

It should be understood that the concentrating device 16 may be disposedat any convenient position along the drill pipe 12 when suflicientanchor pipe 18 is employed to engage the bottom of the well.

Referring now more specifically to Figure 2, it will be apparent thatthe concentrating device indicated at 16 consists of a plurality ofelements. Thus, there is provided a cylindrical or sleeve member 20which in its upper end has a chamber 22 which slidably and rotatablyreceives a cylindrical member 24 which is secured to the lower end ofthe tubular drill stem 12 and also is fixedly secured to the upper endof an inner tubular member 26 which extends into the interior of thesleeve member 20. A suitable internal flange or guide 28 is provided forjournaling the inner tubular member 26 within the upper end of thesleeve member 20 and performs other functions indicated hereinafter. Atany convenient position adjacent its lower end, the sleeve member 20 hasfixedly secured thereto an external flange or plate 30, and a formationpacker 32 is movably positioned upon the sleeve member 20 below theflange or collar 30 and upon its lower surface is engaged by a movablecollar member 34 which is slidable upon the exterior of the sleevemember 20.

Slidably received upon the lower end of the sleeve 20, is a lower casingmember 36 to the lower end of which is secured the anchor pipe 18. Aplurality of suitable outlet apertures 37 and a suitable longitudinalslot 38 are provided in the lower casing member 36, the slot receiving apin 40 carried upon the exterior of the lowermost portion of the sleeve20 whereby the member 36 is retained upon the sleeve 20 and preventedfrom relative rotation thereon but is allowed a limited vertical oraxial movement with respect to the sleeve 20. The upper end of the lowercasing 36 abuts the member 34 whereby when suflicient weight of thedrill stem 12 rests upon the anchor pipe 18 upon the bottom of the wellbore 14, this weight applied by the members 30 and 34 to the formationpacker 32 will radially expand the latter, as shown in Figure l, tocause engagement of the same with the walls of the well bore and thusprevent rotation of the packer and the exterior elements of theconcentrator 16 which are fixedly attached thereto. If desired, thepacker 32 may constitute a fluid tight seal in the well bore, althoughfor the basic purpose of this invention, it is sutficient that thepacker shall prevent rotation of the sleeve 28 and hold the samestationary during rotation of the drill stem 12 and the inner tubemember 26 asset forth hereinafter.

As will be more readily apparent from Figures 2 and 12, the innertubular member 26 is provided in its upper portion with a suitableaperture or port forming an inlet 42 which opens into the interior ofthe sleeve 20 below the partition 28 therein. This inlet thusestablishes communication between the interior of the drill stem 12 andthe annular chamber or space 44disposed between the sleeve 20 and theaxially disposed tubular member 26 therein and also with the interior ofthe tubular member 36.

A spiral vane 46 constituting a spiral conveyor screw is integrallyformed upon the tubular member 26 and extends throughout any desiredportion of the length of the same, it being observed that this conveyorscrew 46 is of such size that its periphery will contact the innersurface of the tubular sleeve 20, while the pitch of the screw mayprogressively decrease from its upper to its lower end, although this isnot essential to the operation of this invention. It will be apparentthat when the drill stem is rotated, the conveyor screw 46 will rotatetherewith within the chamber 44, constituting an impeller for thematerial within the sleeve as set forth hereinafter. The sleeve 20, asshown more clearly in Figures 3 and 4, is provided with a plurality ofapertures or ports 48 therein. These apertures may be arranged in anydesired pattern and over any desired portion of the cylindrical surfaceof the sleeve 20, and they may be of any desired shape or size.Preferably, however, these ports are funnel-shaped or conical, havingtheir apex portions 50 opening into the interior of the sleeve 20 andinto the chamber 44, and having their discharge or base portions 52enlarged and disposed upon the exterior of the sleeve.

The operation of the apparatus as described above is as follows. Bymeans of the conventional mud pump and associated elements, not shown,drilling fluid containing lost circulation material or drilling mudadditives at any suitable concentration as dictated by conventionalpractice is fed downwardly through the drill stem 12 and is dischargedinto the annular space 44 of the concentrator 16 through the inletapertures 42 in the inner tubular member 26. The drilling mud additive,as referred to herein comprises any undissolved material capable ofbeing mechanically screened from a drilling fluid, and is depicted inthe drawings by the numeral 54. The liquid phase of the drilling mudpasses from the annular chamber 44 through the apertures 48 of thesleeve 20 and out of the concentrator 16 into the well bore 14. Thereduced or apex inner ends of the ports 48 areof such size that althoughthey will permit free passage of drilling fluid, they will oppose orrestrict flow therethrough of the drilling mud additive. It will then beseen that the sleeve 20 of the concentrator 16 functions as a screen forseparating the lost circulation material or at least a substantialportion of the same from the drilling mud which is a fluid carriertherefor.

Consequently, as the additive is screened from and separated from thedrilling mud, it is retained and concen-' trated in the chamber 44. Asthe inner tubular member 26 rotates, the conveyor screw 46 thereon willwipe across and clean the ported cylindrical interior surface of thesleeve 20. Further, the conveyor screw will feed the retained materialdownwardly through the sleeve 20 into the tubular member 36 and out ofthe concentrator 16 through the outlet apertures 37 which, preferably,are larger than or otherwise offer less resistance to the passage ofconcentrated lost circulation material than do-the screening apertures48.

The screening action of the concentrator may be enhanced by theemployment of a variable or other suitable resistance to flow attheseoutlet apertures 37, as set forth hereinafter. However, sufficientscreening action at the screening apertures 48 may be obtained by theinitial employment of conventionally high concentrations of lostcirculation material in a low viscosity drilling mud, by pumpingrelatively large volumes of drilling fluid containing the drilling mudadditive under similar high pressures into the concentrator 16, by theemployment of a conveyor screw of decreasing pitch or incorporatingother apertures 48 offer more resistance to the passage of concentratedlost circulation material than the outlet apertures 37, they offer lessresistance to flow of drilling fluid than do the outlet apertures 37 byvirtue of being disposed higher in the concentrator 16 and nearer themud pumps. The concentrator 16 may in some instances be primed bymanually plugging the same with lost circulation material beforelowering the same into the well bore.

I There will thus be a discharge from the concentrator 16 of highlyconcentrated lost circulation material which .will move towards thiefformations and being of a much greater concentration than could passthrough the pumps and'the mud circulatingsystem will more effectivelysea] the formation.

lt will be apparent that the principle of this invention lostcirculation material while discharging or passing the liquid phase ofthe drilling fluid until the concentrated material is discharged throughthe outlet apertures 37 of the concentrator 16. v

Figure 1 indicates at 54 a concentrated mass of lost circulationmaterial as being discharged from the outlet apertures 37 in the tubularmember 36 into the well bore for sealing porous formations andpreventing loss of drilling mud therein.

Modification of Figure 5 The embodiment of apparatus describedhereinbefore is equally susceptible to use with other arrangements.Thus, instead of the formation packer 32 securing the sleeve againstrotation, an arrangement such as that illustrated in Figure 5 may beemployed.

Thus, a sleeve 60 is provided which is identical with the sleeve 20except that the formation packer 32, the fixed and movable flanges 30and 34 and the lower casing sleeve 36 are omitted. At its lower end, thesleeve 60 is instead provided with serrations or teeth 62 which areadapted to engage the bottom of the well bore 14 and thus anchor thesleeve 60 against rotation in the well. However, this arrangementrmayalso be employed above the bottom of the- Well when used in conjunctionwith anchor pipe 18, by providing a serrated or anchoring foot upon thelower end of the tail pipe. The sleeve 60 is provided with the outletaperture 37, for the discharge of concentrated drilling mud additives,and are identical with the outlet apertures 37 in the tubular sleeve 36as set forth her'einbefore.

Received within the sleeve 69 is the inner tubular member 26, aspreviously described, and having the conveyor screw 46 thereon and theinlet aperture 42, together with the swivel consisting of thecylindrical member 24 rotatable within the chamber 22 disposed above thepartition 28. The sleeve 60 is, of course, apertured at 48 in the samemanner as the sleeve 20 and except for the means .for preventingrotation of the sleeve, is in every respect identical with the sleeve20. Accordingly, a further explanation of the operation of thisarrangement is believed to be unnecessary.

In both of the embodiments of Figures 1-4 and of Figure. 5, theconcentrator is disposed on the lower end of the drill pipe near thebottom of the well or is ;used in conjunction with varied lengths ofanchor pipe. How ever, andas set forth hereinafter, as shown in Figure6, it is possible to, provide a form of concentrator which maybedisposed at any desired elevation within a well bore without the useof anchor pipe and which'is carried by suitable resistance therein andalthough the screening 15 a drill pipe as the latter hangs in the wellbore.

At its lower end, the sleeve 60 is internally threaded, at 61, thesethreads preferably extending from above the uppermost outlet aperture tobelow the lowermost aperture. One or more externally threaded hollowsleeves or rings 63 are engaged in the threads 61, being provided withcentral passages 65 which are of such size as to oppose substantially noresistance to fluid flow therethrough. Alternatively, if desired, thepassages 65 may be of such predetermined size as to effect any desiredresistance to flow. By adjustment of the rings axially of the sleevemember 60, the upper and/or lower edges of the rings may be caused tomask or obstruct the area of the outlet openings 37 to any desiredextent, thereby efiecting a variable adjustable restriction of flowthrough the discharge apertures. Thus, the pressure required to forcethe concentrated lost circulation material from the concentrator, andconsequently the degree of concentration effected upon the material, maybe controllably varied. In this form of restrictor, the adjustment abovementioned will be made before the concentrating device is lowered intothe well bore.

This form of flow restrictor, consisting of the adjustable masking rings63 may be utilized with the embodiment of Figures l4 above mentioned,and also with the forms of Figures 9, l3 and 15.

Modification of Figure 6 Attention is directed more specifically toFigure 6 which shows a means whereby the concentrator may be disposed atany desired position in a well. In this figure, there is illustrated asleeve '70 which, as in the preceding embodiments, has a cylindricalchamber 22 for rotatably and slidably receiving a cylindrical member 24which is fixedly secured to the lower end of the drilling pipe 12 andwhich is also rigidly secured to the upper end of the inner tube 26. Thelatter member is, of course, rotatably journaled in the partition 28which divides the chamber 22 from the annular chamber 44 within thesleeve 70. The inner tubular member 26 is likewise provided with adischarge port 42 which is disposed within the chamber 44, and is alsoprovided with the integral helical screw member 46 as in the precedingembodiments.

However, adjacent its lower end, below the funnelshaped perforations 48,the casing 70 is provided with an expansible formation packer 72. Thelatter is retained between an annular external flange 74 on the lowerend of the casing 70 and an upper flange 76. The packer 72 is providedwith an annular chamber 78 therein which surrounds the imperforate lowerend of the sleeve 70. A

tubular U-shaped conduit 30 has its hollow legs communicating with thechamber 78 within the formation packer 72 and upon its midportion has astationary upstanding tubular neck 82 which is swivelly received withinthe open lower end of the tubular member 20.

Thus, when the outlet course of the fluid from port 42 through the ports4-8 is restricted or plugged as by the clogging with concentrated lostcirculation material of the annular chamber 44, the pressure of thedrilling mud from the interior of the drill pipe 12 is supplied to thestem 82 and to the conduits 80 and from thence into the chamber 78 forexpanding, by hydraulic pressure, the packer '72 into engagement withthe wall of the well bore, thereby holding the sleeve 70 againstrotation. The member 72 is thus a pressure operated holding means whichis intended to perform the same function as the packer 32 or the teeth62 in the preceding embodiments. The sleeve 70 is suitably opened at itslower portion to form the outlet port 84 for discharging theconcentrated lost circulation material. The operation of the screwimpeller 46 is identical with that of the preceding forms, the differ"ences of this latest modification residing in the hydraulic holdingmeans for preventing rotation of the casing 70; and the concept andstructure whereby the concentrator may be disposed at any particularformation through which the well bore passes.

Modification of Figures 7 and 8 In all of the preceding embodiments, itwill be noted that the drill stem itself has been employed as a sourceof power for operating the screw impeller to compress and discharge theconcentration of drilling mud additives from the concentrator unit; andfurther, that the concentrated material is discharged continuouslytherefrom. In Figures 7 and 8, there is disclosed a still furtherapparatus for performing the same general purpose; but using the pumppressure as the contracting and discharging means and for effecting anintermittent or batch discharge of slugs of concentrated material.

Thus, there is provided a sleeve which is adapted to be secured in anysuitable way to the lower end of a drilling stem. The lower end of thesleeve 90 is provided with previously mentioned fluid straining orconcentrating ports 48, and an inner tubular member 92 is disposedaxially and fixedly on the interior of the sleeve 90, being securedtherein as by integral lugs or brackets 94. Adjacent its lower end, thetubular member 92 is provided with a partition 96 through which isslidably received a rod 98 having a piston 100 rigidly secured to theupper end of the same and slidable Within the inner tube 92. Acompression spring 102 is disposed within the member 92 below the piston100 and above the partition 96 for yieldingly urging the piston rod intoits uppermost position as shown in Figure 7. The lower end of the rod 98is screw threaded to adjustably receive the hub 104 of a closure valve106 for closing the open lower end of the sleeve 90. A look nut 108 isemployed to maintain the valve in an adjusted position upon the rod 98.

In this form of the invention, the spring 102 normally retains the valvein closed position whereby the lost circulation material passing downthe drill stem into the upper end of the sleeve 90 will accumulate andbecome concentrated in the perforated lower end of the sleeve 90 abovethe closed valve member 106. This concentration will continue, as theliquid phase of the drilling mud passes through the screen ports 48,leaving the larger particles of lost circulation material within theseeve. As this collection of material begins to clog and reduce the areaof the ports 48 through which the drilling mud passes, the pump pressureupon the drilling fluid will increase until such time as the valve 106is opened by this increasing pressure against the resistance of thespring 102 as shown in Figure 8, and the concentrated material will bedischarged under the pump pressure as a slug.

It will thus be apparent that the pressure will periodically increaseuntil such time as the same is sufficient to open the valve, whereuponthe concentrated mass of lost circulation material will beintermittently discharged in slugs or batches. In this form of theapparatus, the concentration and quantity of material discharged and thefrequency of the discharging operations is regulated by the pumpingpressure and volume and the compression of the spring 102, the latterbeing ad'ustable as to its strength by varying the position of the hub104, valve 106 and nut 108 upon the threaded end of the rod 98.

Modification of Figure 9 Still another form of intermittentlydischarging concentrating and pump pressure actuated device is disclosedin Figure 9. In this form, the attachment 109, fixedly attached in anysuitable manner on the lower end of the drill stem 12, terminates in aspring closed check valve 110 and is provided with a sleeve 112 slidablethereon which has a suitable longitudinal slot 114 in which is engaged apin 115 carried by the extension or attachment 109, this pin permittinga limited longitudinal movement of the sleeve 112 but preventingrotation of same relative to the drill stem. A compression spring 116may be secured to the drill stem extension 109 in any suitable mannerand at its lower end bears against the upper end of the sleeve 112 forurging the latter downwardly upon the drill stem extension 109, as shownin Figure 9.

Below the end of the drill stem extension 109 which contains thenon-return check valve assembly 110, the sleeve 112 is provided with theusual funnel-shaped or conical strainer or screening perforations 48previously described. Slidably received within the open lower end of thesleeve 112 is a cylindrical plunger 117 having an externally flangedclosed lower end 118 and a compression spring 120 interposed betweenthis flange and the bottom of the sleeve 112. This spring urges theplunger 117 downwardly with respect to the sleeve 112. Movement of theplunger is limited by pins 121 and longitudinal slots 123 similar to 115and 114, as previously described.

The plunger 117 is provided with a port or set of ports 122 which isadapted to move into and out of register with corresponding ports 124formed in the lower end of the sleeve 112. The arrangement is such thatwhen the plunger 117 is forced inwardly of the sleeve 112, the ports 122and 124 will register whereby the interior of the sleeve will bedischarged or vented through the aligned ports into the well bore.However, when the plunger is moved outwardly of the sleeve 112 under theinfluence of the spring 120, the ports are moved out of registry,whereby the funnel-shaped apertures 48 will constitute the only means ofexit from the sleeve 112.

In this arrangement, the drilling mud including the lost circulationmaterial will be introduced through the interior of the drill stem 12and the extension 109 into the interior of the sleeve 112. The liquidphase of the drilling mud will pass through the apertures 48 beingstrained therefrom and leaving behind the larger particles of the lostcirculation material. This latter material will accumulate and collectin the chamber between the valve assembly 110 and the closed bottom endof the plunger 117. At suitable selected intervals, either controlledautomatically or manually as desired, the drill stem may be lowereduntil the plunger 117 or an attached length of anchor pipe, not shown,rests upon the bottom of the well, and until the weight of the drillstem causes the plunger 117 to move mwardly of the sleeve 112 againstthe spring 120. When this occurs, the ports 122 and 124 being inregistration, the lost circulation material will be discharged in a slugor batch through these ports 122 and 124 by the forcing action of thedownward movement of the drill pipe extension 109 and attached checkvalve assembly 110 against the uppercompression spring 116 together withthe hydraulic pressure exerted by the mud pumps.

Thus, a highly concentrated mass or batch of the drilling mud additiveis discharged into the well bore for treating leaky formations. As soonas the drill stem is lifted, however, the spring 120 will close theports 122 and 124, the upper spring 116 will force the sleeve 112downward with respect to the drill pipe extension 109 and attached checkvalve assembly 110 thereby re-exposing the cleaned screening apertures48 for repeating the straining phase of the operation. The weight of anyanchor pipe which may be employed will assist the springs 120 and 116 inperforming this function of resetting the device.

The form of adjustable flow restrictor disclosed in Figure may also beincorporated into this embodiment. Thus, the rings 63 of Figure 5 may bescrew threadedly engaged in the hollow plunger 117 for controlling theports 122 thereof in the samemanner disclosed in connection with theports 37 of Figure 5. In this arrangement, while the ports 22 arecontinuously held open by the weight of the drill stem while the head118 is on the bottom of the well bore, the adjustable rings 63 willprovide an adjustable control of the degree of concentration of thematerial passing from the ports 122, 124.

In this embodiment, it is possible to produce an initial discharge of aplug having a maximum concentration of material by causing the weight ofthe drill stem to open the ports 122, 124 and thereafter cause acontinuous discharge of a different concentration of lost circulationmaterial to supplement the action of the plug initially discharged.

Modification. of Figure 10 Shown in Figure 10 is a basic form ofconcentrating device which illustrates the fundamental principles of theinvention and which consists of a section of pipe of any desired length,open at both ends and perforated with any number of screening apertures48 of any size or shape. The concentrator, as shown in the figure,employs the previously mentioned, preferred, conical apertures 48 whichwill efliciently screen lost circulation material from a drilling fluidand which are less likely to become clogged with the drilling mudadditive. It should be understood that very high concentrations of lostcirculation material may be obtained and efiectively used to seal porousthief formations by the employment of this basic concentrator.

When this concentrating device is attached to and included between anupper and a lower section of drill pipe conventionally disposed within awell bore, thereby forming a perforated section of the drill stern anddrilling fluid is pumped into the string, which is open at its lowermostend, the drilling mud will tend to follow the course of least resistancethrough the screening apertures 48 since more pressure is required topump the same out the lowermost open end of the drill stem. Therefore,should the drilling fluid contain lost circulation material, it isobvious that the drilling mud additive may be screened from the drillingfluid, retained and concentrated within the string as the drilling mudleaves the device through the screening apertures 48.

It is readily apparent that the efliciency of this screening andconcentrating action may be increased by increasing the area of port ofthe screening apertures 48, thus decreasing the resistance to flowthrough the same. This may be accomplished by increasing the number ofapertures 48 or the size thereof. The screening and concentrating actionmay also be augmented by increasing the resistance to flow below thescreening apertures 48 as by placing the concentrator higher in thedrill string or including a suitable restriction below the concentratoras set forth more fully hereinafter. The lower end of the sleeve or pipe130 is internally threaded at 131 to receive the externally threadedmetering bushing or sleeve 133 which has an aperture 135 of apredetermined area. It is contemplated that plugs having meteringapertures of different areas may be interchangeably inserted in thesleeve 130 to vary the resistance to flow therethrough.

Such restriction may also be in the form of a suitable drill bit whichwill permit the drilling operation during the employment of aconcentrating device.

As the concentration of lost circulation material is formed by thisarrangement, it is forced downwardly through the lower section of drillpipe, which is disposed below the concentrator, and out through the openlowermost end of the drill string into the well bore by the hydraulicpressure exerted by the mud pumps.

It will be noted that as the lower section of drill pipe, which isdisposed below the concentrator, becomes filled with the downwardlymoving highly concentrated lost circulation material, the resultingfriction will constitute a resistance below the screening apertures 48and augment the screening and concentrating action as previouslydescribed. Therefore, the efiiciency of this arrangement is necessarilylimited to the pressures available for discharging the concentrateddrilling mud additive out of the string through the outlet at its openlowermost end. Otherwise, the whole lower section of the string maybecome plugged with the concentration, requiring operations to bediscontinued. However, this form of concentrating device may not only beplaced at any position within the pipe string, but may be attached atthe lowermost end of the same.

Figure 11 is very similar to the embodiment of Figure 10, but indicatesa sleeve 140 having a restriction 142 of any form below the screeningapertures 48 for increasing the efficiency of the screening andconcentrating action previously described.

Reference has been made hereinbefore to provision for the adjustablerestricting or throttling of flow of the concentrated lost circulationmaterial through the discharge apertures of the various embodiments ofapparatuses disclosed herein as a means for controlling the degree ofconcentration of the lost circulation material; and/ or the frequency orrate of its discharge.

In both of the embodiments of Figures and 11, as well as in that ofFigure 5, the flow restrictors are of the preset adjustable type, beingapplied prior to lowering of the concentrating device in the well bore.This restrictor may be included in any of the concentrating devices ofFigures 6, 7 and 11.

Modification of Figures 13 and 14 This embodiment very closely resemblesthe form of the invention disclosed in Figure 5, including a generallycylindrical casing 150 having a partition 152 in its upper portion todefine a chamber 154 thereabove in which is rotatably mounted aswivelling connection 156 by means of which the drill stem 12 isconnected to the upper end of the inner tube 158 having the conveyorblades 160 thereon. The portion of the sleeve below the partition 152 isprovided with the previously mentioned strainer or screening apertures48 for the purposes previously set forth. Just below the partition 152,the tube 158 is provided with one or more discharge apertures 162 bymeans of which drilling fluid with lost circulation material admixedtherewith may be discharged into the chamber 164 disposed beneath thepartition 152.

At its lower end, the perforated portion of the sleeve 150 isdiametrically enlarged, as at 166, to form a valve chamber forintermittently discharging slugs or batches of concentrated lostcirculation material, as set forth hereinafter. The open lower end ofthe enlargement 166 is internally threaded, as at 168, for receiving theexternally threaded neck 170 of an internally threaded sleeve or bushing172. The latter is provided with one or more discharge apertures 174extending through the side wall of the same, and externally threadedrings 176 are threadedly engaged in the internally threaded sleeve 172and are axially adjustable therein to adjustably mask or throttle theoutlet openings 174.

The lower edge of the sleeve 172 may be either open or closed, asdesired, and is provided with a plurality of serrations 178 whereby thelower end of the concentrator may be securely held in a stationarymanner upon the bottom of a well bore to prevent rotation of the same.

Within the enlarged lower end 166, there is provided a valve assemblyfor controlling the intermittent discharge of slugs of concentratedmaterial. Conveniently, as will be apparent from Figure 14, this valveassembly consists of a stationary, preferably semi-circular plate 180which is secured to a portion of the inner Wall of the enlarged housingportion 166, and has a substantially diametrically extending edge acrossthe interior of the housing.

Cooperation with the stationary valve member 180 is a similar plate 182which is welded or otherwise rigidly secured to the lower end of thetube 158 for rotation therewith. As will be apparent from Figure 13, theadjacent edges of the plates 180 and 182 are disposed in overlappingrelation so that as the valve member 182 rotates, it will alternatelyclose and open the passage by the stationary valve member 180.

As will be noted, the cross-sectional area of the mem- "ber 166 has beenconsiderably enlarged'with respect'to that of the chamber 164 in orderthat there shall be ample passage area to permit passage of theconcentrated material from the chamber 164 during the intermittentperiods when the valve is opened.

It will be, of course, understood that the valve plates and 182 may beconstructed to provide any desired area of passage therebetween, andalso to provide any desired duration during which the passage is open aswell as any desired interval between the opening and closing of thepassage.

Except for the intermittent valve action in releasing the concentratedmaterial in the form of slugs from the chamber 164, the arrangement ofFigures 13 and 14 may be considered as identical with that of Figure 5,previously described.

Modification of Figure 15 In Figure 15, there is disclosed anapplication of the principles of Figures 5 and 13 to the arrangement ofFigure 2. The numeral discloses the lower portion of a casingcorresponding to the casing 20 of Figure 2, and in which is received thelower end of the inner tube 26 having the helical auger screw'46thereon, as previously described. At its lower end, the sleeve 190 isexternally threaded, as at 192, and is internally threaded as at 194. Abushing 196 is internally threaded, as at 198, for screw threadedengagement upon the threads 192 of the sleeve 1%. At its lower end, thebushing 196 is diametrically reduced to provide a depending portion 200,to which any desired length of tail or anchor pipe 202 may be secured.This latter pipe is preferably closed at its-lower end, as shown, andthe interior of the sleeve 190 communicates with the well bore throughthe discharge apertures 204.

A pair of externally threaded rings 206 and 208 are provided forengagement with the threaded portions 194 and 198 for adjustably maskingor controlling the discharge apertures 204. These rings function in thesame manner as previously referred to control rings 63 in the embodimentof Figure 5.

A rotary valve member consisting of a fixed valve plate 210 and a rotaryvalve plate 212 is provided. These valve plates are arranged in the samemanner and correspond to the valve plates 180 and 182 of the form ofFigure 13.

It is believed that the operation of this form will be now clearlyunderstood from the previous explanation with regard to Figures 5 and13. By means of the tail pipe 202, the discharge openings 204 may beplaced at any desired position within a well bore, and the size of theseopenings may be varied by the control rings 206 and 208 in order thatthe rotary valve assembly 210, 212 may periodically time the dischargeof batches or slugs of concentrated lost circulation material from theconcentrator into the well bore.

Modification of Figures 16-I9 A still further form of concentratingdevice is disclosed in Figures 16-19. In this form, there is provided asleeve 220 which has its upper portion imperforate and provided with aswivel assembly, indicated generally by the numeral 222 and which isshown in detail in Figure 18. Throughout any desired proportion of itslength, the sleeve 220 is provided with the previously mentionedstrainer or screening apertures 48, and a stem 26 which may be eithertubular or solid is disposed in the sleeve and is provided with theconveyor blade 46, all as previously set forth in connection with theother embodiments of the invention.

As shown best in Figure 17, the lower end of the casing 220 isinternally threaded at 224 for the reception of a cylindrical body 226.The latter is provided with a pair of elongated slots 228 and a centralaxially extending dividing web or rib 230 is provided therein. The

13 I the slots to provide a transverse passage 232 which constitutes adischarge port for the cylindrical body 226. At its lower end, thecylindrical body 226 is provided with an open bore 234 which is normallyclosed by a cap 236 having a plurality of fins 238 upon its bottomsurface. It will thus be seen that the body 226 and the cap 236constitute a closure means for the open lower end of the concentratorsleeve 220, as shown in Figure, 17. Alternatively, as shown in Figure19, the sleeve 220 may be closed at its lower end as by a plug 240 for apurpose which will be subsequently set forth.

Referring now more particularly to Figure 18, it will be seen that theswivel assembly 222 comprises a hollow mandrel 242 which intermediateits ends is provided with an annular enlargement in the form of a ringor collar 244. This collar is slidably received in the bore of thesleeve 220, and a rubber O-ring 246 is seated in cooperating peripheralgrooves in the wall of the sleeve and of the collar 244, to preventleakage of drilling fluid past the collar. Disposed above the collar isan antifriction bearing assembly 248 of any desiredcharacter which restsupon the collar and is retained therein by the lower externally threadedportion 250 of the gland 252. The gland surrounds the mandrel and at itsupper open end is provided with a chamber 254 in which is received afurther antifriction bearing assembly 256 which surrounds the mandreland which is retained in the chamber by the lower end of the packing nut258. An O-ring 260 is also provided between the packing nut 258 and theWall of the chamber 254 in order to prevent leakage of fluid throughthis packing assembly. The packing nut 258 is threadedly engaged uponthe mandrel and is retained thereon as by a locking nut 262 which isprovided with a setscrew 264. The mandrel 242 at its upper end isconnected in any desired manner to the drill stem 12 previouslymentioned, whereby drilling fluid having lost circulation materialadmixed therewith may be supplied through the mandrel into the interiorof the sleeve 220.

At its lower end, the mandrel 242 extends into the chamber 4-4 formedbetween the conveyor shaft 26 and the wall of the casing 220, and isprovided with one or more apertures or ports 266 for discharging fluidinto the chamber 44. The upper end of the conveyor shaft 26, whetherhollow or solid, is received within and fixedly secured to the openlower end of the mandrel, as shown in Figure 18.

It will thus be apparent that the conveyor screw is journaled in thecasing in such a manner that the casing may be readily held stationaryin the well bore in any of the manners previously described while therotation of the drill stem will, in turn, cause rotation of theconveyor.

It is to be understood that the above described swivelling arrangementdisclosed in Figure 18 may be readily applied at any of the swivelspreviously mentioned in connection with the other embodiments of theinvention.

Method of operation When in the drilling of well bores, a porous orthief formation is encountered of such character as to requireextraordinary concentrations of lostvcirculation material in order toseal the same and regain circulation, the following method may beemployed.

A concentrator sleeve is primed and then attached to the end of thedrill string. The sleeve may be primed by closing the lower end of theconcentrator sleeve, as by the closure plug 240, and then coupling thesleeve to a mud circulating system. As the drilling fluid containing thelost circulation material admixed therewith is circulated through theconcentrator, the liquid phase of the same will be strained through thescreening openings 48, leaving the larger particles of the additive inthe casing. This is continued until the desired concentration of lostcirculation material is attained, and for this purpose, 1'0- 14 tationmay be imparted to the screw for further compressing and compacting suchmaterial. With the concentrator thus primed, the closure plug 240 isremoved and the appropriate connection made in accordance with thevarious embodiments set forth in this application for the discharge ofthe concentrated material therefrom. With the primed concentratingdevice then applied to the end of a drill stem, the latter is lowered inthe well bore until the concentrator device is at the location at whichthe loss of circulation occurred. Thereafter, as drilling fluid issupplied by the mud circulating system, rotation of the drill stem willcause the conveyor screw to force the batch of concentrated materialfrom the device into the well bore where it will be carried into thefissures and crevices which it is intended to seal. It will be notedthat in addition to this initial slug or plug of material dischargedfrom the concentrator, the continued operation of the latter will causea subsequent and sequential flow of the concentrated lost circulationmaterial from the device into the well bore, either continuously or inintermittent batches, depending upon the type of apparatus hereinbeforedisclosed, which is employed. In order to facilitate the action of thelost circulation material in sealing the leak, the device may be raisedor lowered periodically during its operation so as to distribute thematerial along a selected portion of the height of the well bore.

It is an important characteristic of this invention that by means of acontinuous flow of drilling mud containing lost circulation materialadmixed therewith in a proportion in accordance with conventionalpractice and capacity of existing conventional mud pumping equipment,there may be selectively secured very highly concentrated batches oflost circulation material; and these batches may be dischargedintermittently at regular intervals into the formation to be sealed, ormay be discharged continuously at a lesser concentration; or,combinations of the same may be effected.

In some instances, where a fine porous formation is encountered, it maybe found preferable to under-ream the same in order that when theformation is sealed, the passage of the drill bit into the bore toresume its drilling operation may not scrape any of the sealing materialadhering as a thin sheath to the interior of the well bore.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation as shown anddescribed, and accordingly, all suitable modifications and equivalentsmay be resorted to, falling within the scope of the appended claims.

What is claimed as new is as follows:

1. A method of preventing the loss of circulating drilling fluid from awell bore into a porous formation, which comprises inserting into a wellbore having drilling fluid therein a pipe containing a discrete batch oflost circulation material, introducing into said pipe and circulatingthrough said pipe and well bore drilling fluid having lost circulationmaterial admixed therewith in a lesser proportion than that of saiddiscrete batch and thereby displacing said batch from the pipe into thewell bore, conveying by said circulating drilling fluid said batch fro-msaid pipe into said porous formation and thereby initiating sealing ofthe latter, completing sealing of the porous formation by theapplication thereinto of the admixed lost circulation material in saiddrilling fluid.

2. A method of preventing the loss of circulating drilling fluid from awell bore into a porous formation, which comprises inserting into a wellbore having drilling fluid therein a pipe containing a discrete batch oflost circulation material, introducing into said pipe and circulatingthrough said pipe and well bore drilling fluid having lost circulationmaterial admixed therewith in a.

lesser proportion than that of said discrete batch and therebydisplacing said batch from the pipe into the well bore, straining theintroduced drilling fluid during its passage through said pipe andremoving therefrom a portion of the drilling fluid thereby increasingthe concentration of the lost circulation material in the remainder ofthe drilling fluid, conveying by said circulating drilling fluid saidbatch from said pipe into said porous formation and thereby initiatingsealing of the latter, completing sealing of the porous formation by theapplication thereinto of the admixed lost circulation material in saidconcentrated remainder of said drilling fluid.

3. The method of claim 2 wherein said step of displacing said batch fromthe pipe into the well bore includes the steps of alternately preventingand effecting flow of said concentrated remainder from said pipe into'said well bore at uniform time intervals whereby said concentratedremainder is intermittently discharged from said pipe into said wellbore at uniform time intervals.

4. An apparatus for preventing loss of a circulating drilling fluid froma well bore into an adjoining porous formation comprising; a pipedisposed in a well bore, means introducing into said pipe andcirculating through said pipe and well bore a drilling fluid having alost circulation material admixed therewith, a concentrator connected tosaid pipe and receiving drilling fluid therefrom for increasing in aportion of said drilling fluid the proportion of lost circulationmaterial over the proportion of the latter in said introduced drillingfluid, said concentrator having a discharge passage for said portionopening into said well bore, said concentrator including a spiralconveyor and means associated therewith for straining drilling fluidfrom the introduced drilling fluid admixed with lost circulationmaterial, means causing rotation of said spiral conveyor, valve meansconnected to and driven by said spiral conveyor and disposed in andcontrolling said passage for effecting intermittent, periodic dischargeof said portion of drilling fluid in separate batches from saidconcentrator into said well bore.

5. The combination of claim 4 wherein said valve means comprises astationary plate partially closing said passage and a movable plateconnected to said spiral conveyor and slidably engaged and cooperatingwith said stationary plate for periodically completely closing saidpassage.

6. The combination of claim 4 wherein said introducing means includes apassage in said spiral conveyor having an exit into said concentrator.

7. The combination of claim 4 including means anchoring saidconcentrator against rotation in a well bore.

8. The combination of claim 4 wherein said rotation causing means forsaid spiral conveyor comprises means mounting the latter upon andconnecting the latter to said pipe and means for rotating said pipe.

9. The method of claim 2 wherein the step of straining the drillingfluid is performed continuously and without interruption and whereinsaid step of displacing said batch from said pipe into the well boreincludes the steps of alternately preventing and effecting the dischargeof said concentrated remainder from said pipe into said Well bore atuniform time intervals whereby said concentrated remainder isintermittently and periodically discharged from said pipe into said wellbore as discrete slugs.

10. The method of claim 2 wherein the step of straining the drillingfluid is performed continuously and without interruption and whereinsaid step of displacing said batch from said pipe into the well boreincludes the steps of alternately preventing and effecting the dischargeof said concentrated remainder from said pipe into said well bore atuniform time intervals whereby said concentrated remainder isintermittently and periodically 16 discharged from said pipe into saidwell bore as discrete slugs, and at uniform time intervals.

11. The method of claim 2 wherein the step of straining the drillingfluid is performed continuously and without interruption and whereinsaid step of displacing said batch from said pipe into the well boreincludes the steps of alternately preventing and effecting the dischargeof said concentrated remainder from said pipe into said well bore atuniform time intervals whereby said concentrated remainder isintermittently and periodically discharged from said pipe into said wellbore as discrete slugs, and at uniform time intervals, and in uniformquantities.

12. The combination of claim 4 including a pair of discharge portsdisposed in spaced relation in said discharge passage each communicatingwith said discharge passage and spaced longitudinally thereof anddischarging said separate batches at spaced locations in said well bore.

13. The combination of claim 12 including a flow regulator disposed insaid discharge passage between said discharge ports and proportioningflow of said batches therethrough.

14. A concentrator for use in a well bore for increasing the proportionof a lost circulation material in a portion of a circulating drillingfluid having a lost circulation material admixed therewith, comprising;a casing having a cylindrical chamber therein with fluid inlet means andfluid outlet means therefor, said chamber having a wall with straineropenings therethrough, a spiral conveyor mounted in said casing andfeeding drilling fluid from said inlet means to said outlet means andstraining drilling fluid from said chamber through said straineropenings and thereby effecting an increased proportion of lostcirculation material in the portion of the drilling fluid dischargedfrom said outlet means, means for causing rotation of said spiralconveyor in said chamber, valve means establishing controlledcommunication between said chamber and the exterior of said casing foreffecting intermittent, period discharge of said portion of drillingfluid from said outlet means in uniform amounts and at uniform timeintervals, means operatively connecting said valve means to said spiralconveyor for actuation by the latter.

15. The combination of claim 14 including a valve housing for said valvemeans mounted upon said casing.

16. The combination of claim 14 including a valve housing for said valvemeans mounted upon said casing, said valve means comprising a stationaryplate in said housing partially obstructing flow therethrough and a.movable plate slidably engaging and cooperating with said stationaryplate to periodically stop flow through said housing and periodicallystopping flow through said outlet means.

17. The combination of claim 16 wherein said movable plate is attachedto said spiral conveyor.

18. The combination of claim 14 including a valve housing for said valvemeans mounted upon said casing,

said housing including means for anchoring the latter against rotationin a well bore.

19. The combination of claim 14 wherein said spiral conveyor has a fluidpassage opening into said chamber, said passage comprising part of saidfluid inlet means.

References Cited in the file of this patent UNITED STATES PATENTS2,083,625 White June 15, 1937 2,167,190 Vietti July 25, 1939 2,187,895Sanders Jan. 23, 1940 2,207,334 Reynolds et al. July 9, 1940 2,652,117Arendt et al Sept. 15, 1953

